fans

Assimilation lights give off a lot of heat which stays at the top of the greenhouse when you would rather have it down near the crop. And closed screens also bump up the temperature too much. Fresh Valley in the south-east of the Netherlands has solved both these problems with a combination of two vertical fans. After a successful trial, tomato grower Bert van den Brand has also installed the system at his second site where it is enabling him to limit light emissions with no side-effects.

When Bert van den Brand increased the assimilation lighting in his nursery in Uden from 8,000 to 13,000 lux in late 2014, he encountered a problem. “We are right next door to a residential area there so we have to use screens to prevent light emissions. But with such high light levels the night-time temperature rises so high that it affects your 24-hour temperature. So you end up with thin, puny plants, poor fruit setting and the risk of scorching on the shoot apex”, he says. He wanted to find a relatively simple solution to the problem.
As it happened, an energy efficiency trial involving a combination of two fans had been running at his Maasbree site since the beginning of that year, run by Wageningen University & Research in collaboration with Dutch suppliers Vostermans Ventilation and Hint Installatietechniek. The results were so good that the grower decided to try out the system at his site in Uden as well.

Own brand

Fresh Valley has two sites: 2.7 hectares in Uden and 6.3 hectares in Siberië, Maasbree. The nursery mainly grows Juanita, a small, sweet truss tomato sold under their own brand name, L’Amuse. It also supplies Kumato, a golden-brown tomato grown by other growers. Half the area in Maasbree is lit with 10,000 lux and the other half with 13,000 lux. Half the power needed for this system comes from the nursery’s own CHP unit and the rest is bought in. They opted for this arrangement to avoid generating a lot of excess heat.
The combination of fans was left in place after the trial (3,000 m2). “The bottom fan, a Multifan V-FloFan, draws the cold air upwards from below and distributes it horizontally so that it passes along the lights and warms up. When the lights are on, this fan is always running,” van den Brand says. It’s the same at the Uden site.

Better temperature distribution

The top (axial) fan draws cold, dry air downwards through the closed screen. This air bounces off a plate and is then distributed by the bottom fan. The top fan is only used if it gets too hot or too humid under the screen,” says Guus Vostermans, sales engineer at the company of the same name.
The result achieved with the combination, named Ventilation Jet, is better mixing of the greenhouse air and therefore fewer horizontal and vertical temperature fluctuations. Van den Brand: “Before the trial I had not expected it to work as well as it did. But not only did Wageningen University & Research’s measurements indicate better temperature distribution, the crop is also more even.”
There are 50 fan combinations per hectare in Maasbree and 11 per hectare in Uden. Because the top fans there are double capacity, that works out at the equivalent of 22 per hectare. So that is still quite a lot fewer. “In Uden we have an Obscura blackout screen that is 95% closed. So you actually always have a small gap of five percent. That’s why we could get by with fewer there,” he says. They also have ducts with fans hanging under the gutters, which also help improve air circulation. “If we didn’t have those, we would need more fan combinations.”

Preventing light emissions

Van den Brand has not yet decided to kit out the whole greenhouse in Maasbree with the system. That will probably only happen when the screens need replacing. At the time of the trial, which focused on energy saving, two highly insulating screens were installed in the section with the fans. Because of the low post height (4.5 m), they run across the same wire bed so they can’t both be closed at the same time. There is a blackout screen (XLS 10 Revolux) and a transparent screen (XLS SL 99 Revolux W/W).
But saving energy is not van den Brand’s main objective. “Our primary concern at Uden is to prevent light emissions. The Ventilation Jet is the only way we can keep the air cool enough in our situation. The second argument in its favour is a more even climate.”

Energy savings

The system does in fact deliver energy savings. Van den Brand puts the savings in the section in Maasbree (3,000 m2) at around 10-15% in winter, thanks to a lower minimum pipe temperature, fewer gaps and less venting. “The minimum pipe temperature is about 4°C lower, so 36°C instead of 40°C, for example. But the plant always comes first. If it needs 40°C, it gets 40°C.”
The transparent screen stays closed for the first eight weeks of cultivation. “This also benefits the plant. With the darker screen we don’t need to leave gaps at night up to an outside temperature of 12°C, and you hardly ever get that in winter”, he says.
Without the fans he would have to vent more when the screen is closed. “That’s not ideal, of course: you’re getting rid of heat and wasting energy”, he says.

Mixed feelings about NGG

So there is evidence that this system does save energy. But as already mentioned, that is not van den Brand’s primary concern. He mainly tends to sidestep Next Generation Growing (NGG): “With an unlit greenhouse, NGG can save you a lot of energy, but we have lighting everywhere. There are definitely good things in the NGG approach, but I can also see accidents happening. You take big risks to save a few cubic metres of gas, but that can be at the expense of quality and flavour, as flavour can deteriorate if you inhibit transpiration. We can’t allow that to happen with our own brand. So we have very mixed feelings about NGG. It depends a lot on whether you are production- and cost-oriented or market-oriented, as we are. We would rather not risk it.”
Fresh Valley was one of the first nurseries to use vertical fans. The concept has been refined since then. Vostermans says that following customer feedback they reduced the noise level: “People found it particularly annoying at harvest time and while working on the crop. The current generation is quieter and also a lot more energy-efficient.”

Summary

Fresh Valley uses a combination of two vertical fans. The bottom fan is always running when the assimilation lights are on. It draws cold air upwards from below and mixes it with the warm air at the top of the greenhouse. The second fan draws cold, dry air downwards through the closed screen. Together they create a better greenhouse climate with fewer temperature fluctuations and save energy as well. At one site, the main reason for installing the fan system was to prevent light emissions without causing problems.

Golden Fresh Farms, based in Wapakoneta, Ohio, USA, is a high-tech tomato producer selling to leading grocery retailers in North America. In Greenhouses spoke to Luis Chibante, president and CEO of the company, to learn more about the company’s activities and high-quality, innovative approach.

The history of Golden Fresh Farms, managed by Luis Chibante (president) and Paul Mastronardi (vice president), began around four years ago. It was set up as a sister company of Golden Acre Farms near Kingsville, Ontario, Canada. “When looking to expand our operations,” explains Chibante, “I decided to build a new company here in Wapakoneta, Ohio, for several reasons. Firstly, this location in the Midwest of the USA gives us access to around 200 million people within easy driving distance, which is beneficial in terms of logistics and shelf life. Secondly, the winters are cold here, which we actually like because it helps to keep pests down to a minimum without spraying, and we aim for pesticide-free as much as we can. And thirdly, there is a high energy availability at low cost in Ohio. In fact, we don’t generate our own energy because it makes better financial sense to buy it in than produce it ourselves. That’s a big difference from Canada.”

Locally grown

Sustainability is an important theme for the company, which has a strong focus on quality and freshness. “We strive to grow the best products using sustainable methods. We’re positioned at the higher end of the market, but once our retail customers know that we’re an efficient greenhouse company they’re happy to enter into long-term partnerships with us,” comments Luis.
Nowadays, both retailers and consumers are increasingly realizing that cheaper is not always the best approach. It’s more a matter of how you can improve your product quality, taste, longevity and appearance. That enables you to sell 100% of your product rather than just 80% of your product with the other 20% going to waste, and waste is such a huge issue in retail. “So retailers might have to pay us a bit more, but they’re ultimately profiting a lot more. It took us a little while to create that new mindset among our customers, but they’ve now seen that it achieves real results. And the consumer is actually the winner.”
The company is already selling to most of the big retailers in the USA: Kroger, Meijer, Metro, Sobeys. “In fact, now that we’re a US company a lot of retailers are actually coming to us saying they want to stock our product because it’s locally grown and the sustainability and the product quality are better than they’re used to.”

Tradition of innovation

Now that the first phase of the construction project has been completed, Golden Fresh Farms is a 7 hectare hydroponic greenhouse facility with 75 employees. It has a production capacity of approximately 200,000 tomato plants and an annual yield of 4.5 million kilos of three types of tomatoes: beef, cluster and cocktail. At the end of expansion phases 2 and 3, which will take another 10 to 15 years, the facility will comprise around 32 hectares.
Chibante continues: “To ensure freshness and quality, it’s a very high-tech facility with a fully integrated operation from seeding and harvesting to fully automated packaging and shipping. We’ve definitely benefited from the tradition of innovation at Golden Acre Farms in Canada. That was one of the first greenhouses in North America to work with a trough system. We’re talking 18 years ago.”
In another example, before diffuse glass was invented, Golden Acre Farms was actually one of the first greenhouses in Canada to install two curtain systems, one for energy and one for diffuse light. “So we were doing diffusion before it even became popular. And then five or six years ago, we were one of the first high-tech facilities in North America in terms of lighting and robotised packaging.”

Improving efficiency

The company Thermo Energy Systems has played a key role in those innovative developments, and was instrumental in the design and construction process of the Ohio facility too. “I’ve known Henry Froese, president of the company, for more than 20 years. Even back in those early days we were both very interested in improving efficiency, so we bounced ideas off of one another – him as an engineer and me as a grower – to make his company better and to make my company better, and our partnership has evolved ever since,” recalls Chibante.
“He’s done a lot for us in Canada over the years so it was only logical for us to contact him and his company when we were planning this new facility. In the end, they built the whole greenhouse as their first-ever turnkey project. We architected the facility together – it took around a year and a half to do all the drawings – and then we found the right location. The construction work was completed in just eight months, believe it or not. We’ve been able to use all the technical knowledge gained in Canada when designing our Ohio facility.”

Benefit heat from HPS

So it obviously has diffuse glass, energy curtains and Golden Fresh Farms was set up for semi-cooling if the company decides to grow in summertime in the future. “So basically we have everything we need at our fingertips. We work with HPS lighting rather than LEDs, for two main reasons. Firstly, the energy costs are so low in Ohio that LED cost-savings aren’t a consideration, and secondly the winters here are so cold – with night-time temperatures of down to minus 5°C and daytime temperatures of below zero – that we actually benefit from the heat produced by the HPS lighting.”

Pioneering technology

Another innovative solution that Thermo Energy Systems installed at Golden Fresh Farms is a pioneering fan system by Dutch manufacturer Van der Ende Group. The unique setup of the manufacturer’s Enfan horizontal fans in conjunction with the Verti-Fan vertical fan system combines vertical and horizontal airflows to compensate for any temperature and humidity variations.
This maintains an optimal climate throughout the entire greenhouse, activating crop growth while also helping to save energy. “The horizontal fans are common over here but it’s unique to combine them with the vertical system. Everything works on sensors and is fully computer controlled, there’s no manual intervention. The need for constant air circulation depends on so many factors – the climate and light level outside, whether the curtains are closed, whether the HPS lighting is on – and for each factor the computer knows precisely when to implement the fans. This optimally balances the climate from one end of the greenhouse to the other – which is 430 metres in length and has 49 bays of 8.5 metres each – and there’s a constant air flow without any wind effect.”

Further expansion

The first crops were planted in the Golden Fresh Farms greenhouse in February 2017, so the coming season (September 2017-August 2018) will be the first real test, but Golden Fresh Farms’ president is pleased with the initial results. “The production numbers look really good and we’re already seeing results in the crops in terms of quality. In fact, we like the innovative air circulation system so much that we’re planning to install it in our Canadian facility too in the longer term.”
In the meantime, he has got his work cut out supervising the further expansion of the company in its mission to ensure that its US customers continue to receive the freshest, highest-quality, most environmentally sustainable and locally grown produce throughout the year.

Summary

Golden Fresh Farms, based in Wapakoneta, Ohio, USA, has recently completed phase one of what will become an 32 hectare high-tech greenhouse facility for tomatoes. This innovative hydroponic facility includes a pioneering climate control system combining horizontal and vertical fans to achieve optimal airflow the entire length of the greenhouse.

Good air movement in the greenhouse is increasingly important. The principles of Next Generation Growing are closed screens, limited use of the minimum pipe and good air circulation. But how do you prevent a cold dump, a draft, a relative humidity that is too high and temperature differences? Fans that bring air from above a fully closed screen into the greenhouse appear to be the most effective. Dutch growers, Wageningen University & Research and suppliers are working closely on the ‘Monitoring’ project to optimise their utilisation.

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Good air circulation in the greenhouse is an energy efficient alternative to using the minimum pipe rail for growers working with Next Generation Growing. But fans come in many shapes and sizes and how well do they work? They are often not checked to verify if they have the desired effect. Measurement is key: A smoke test quickly shows how the air is moving. Suppliers would like to cooperate and furthermore they recommend that equipment is properly maintained.

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Gardener’s Pride, the tomato nursery belonging to Cock and Marja van Overbeek, is starting to master the principles of Next Generation Growing. The new greenhouse has vertical fans and manager Tim Schinkel is completely in his element because he can manipulate the plant burden. The air movement ensures a steady climate and good moisture control.

At Gardener’s Pride, in Beetgum, the north of the Netherlands, the end of March signals the time for interplanting. The old crop, planted in July 2015, is topped and young grafted, topped plants are ready for the new season. The tomato nursery specialises in small tomatoes up to 20 grams, both loose and on the vine. It grows 14 different varieties of which three are produced in the new greenhouse. These tomatoes are mainly sold to regular retail customers.
This is the third crop since October 2014, when the 55,000 m2 greenhouse equipped for Next Generation Growing was completed. It has a SON-T lighting system of 200 µmol/m2/s that can be switched on over four stages. Cock van Overbeek, owner of the tomato company and manager Tim Schinkel explain the decisions they made.

Open system

In the quest to adopt Next Generation Growing in this new greenhouse, Van Overbeek considered several different systems. He visited colleagues who have air hoses under the gutter but decided he didn’t want so many hoses per bay. Bearing in mind the investment would be high he therefore considered other air circulation systems. In the end he decided on the Ventilation Jet, a vertical unit with two fans. The top fan sucks in cold dry air above the closed screen via an opening below. The lower fan sucks greenhouse air upwards from the crop below and mixes the cold dry air with the greenhouse air that has been warmed mostly due to the lamps.
The roof is of diffuse glass and there is a blackout screen just above which is an energy screen. “I had a good feeling about this open system,” says Van Overbeek, who runs horizontal fans in other sections of the greenhouse. He also wanted to change the way he managed the climate and limit the role of the minimum rail via the pipe rail net.

Teething troubles

Based on these principles Tim Schinkel set to work. Initially it wasn’t that easy and he had to deal with a number of teething troubles during the first winter. It was very difficult to drain off the moisture and the crop began very vegetatively. “It's hard to point to a cause afterwards,” he says. “We suspect that the ground under the new greenhouse was very cold and damp which meant we had to use the minimum tube more often than we wanted.”
More things emerged. The over pressure under the screen and the air movement caused the screen to shift. It had to be weighted down. In addition, the fans tended to swing due to the lightweight fixtures. Also the diameter of the plexiglass disc between the two fans had to be adjusted to enable better mixing of the air (within one meter from the fan) and its distribution through the crop.
Finally, the energy screen was modified to allow a gap to be made above the central path. Smoke tests proved that the air flowed towards the middle of the greenhouse where the greenhouse is the highest. This provided an extra opportunity to move the greenhouse air upwards.

Air movement

Meanwhile, the Ventilation Jets (one per 350 m2, 161 in total), which are interspersed with regular vertical fans, have been properly adjusted. Once again it was smoke tests that showed that the airflow through the crop was now good and was able to take air heated by the lights down through the crop. It worked so well that it was no longer necessary to use the minimum rail during the period of artificial lighting. Heating the greenhouse is now primarily with the growth tube.
“We’d seen previously in the other, conventional greenhouse that the fruits don’t turn colour so well when the fans are turned on. In that section we installed air hoses under the cultivation gutters for extra air movement underneath. In the new greenhouse they turn colour very easily,” explains Schinkel.

First ventilate above the screen

The next step in Next Generation Growing is to fine-tune the climate. The art is to achieve a good climate and save energy at the same time. Schinkel says that the climate in the greenhouse is now much drier than during the first cultivation year. “Due to the adjustments to the fans we can now run at full speed,” he notes. Last year he sometimes saw condensation on the energy cloth at the end of the afternoon. That happens much less now.
If the temperature in the greenhouse rises too much or the air contains too much moisture he first ventilates above the screens, preferably at a low stand on the sheltered side and more on the wind side. This enables the moving airflow to provide the best exchange of greenhouse air and outside air.
The next step is to make a small gap of maximum ten per cent in the energy screen. The blackout screen remains completely closed during the blackout period. It seems that more air exchange takes place through the black out screen than through the energy screen.

Grip on plant balance

The diffuse greenhouse roof results in a more meagre crop, notices the manager. This is probably due to the transmission of a broader light spectrum, including ultraviolet. On warm, sunny days, he tries to keep moisture inside. In addition, he allows the radiation level and radiation sum to determine the 24-hour temperature. This can vary between 17.5 and 19.5ºC in the early spring in the unlit part of the greenhouse. Schinkel: “In this way I can keep a grip on the plant balance. I want the sugars that have built up in the plant to reach all plant parts within 24 hours.”
In this way he is steadily achieving a good plant balance, a slightly lower plant burden and as a result faster ripening of the fruits. He deliberately harvests larger fruits. “We prefer to pick fruits of 16 grams than 13 grams. We have of course a very hardworking crop that requires a lot of labour. We try to keep it as manageable as possible.”

Step towards sustainability

Everything requires effort, says Schinkel. A recent, short but intense, fire in the water house caused panic. Fortunately the damage was limited and the water supply was quickly restored. There are also some new challenges. In the new greenhouse they are currently running a trial with different substrate mixtures in containers, another step towards sustainable production.

Summary

In 2014, Dutch nursery, Gardener’s Pride, built a new greenhouse equipped with vertical fans. These fans and a double screen enable the nursery to apply Next Generation Growing techniques. The first year was not completely flawless due to teething problems. By adjusting the system the crop is now growing as cultivation manager Tim Schinkel intended.

Chrysanthemum grower Maurice van Os, like many Dutch colleagues, has a problem with thrips in the nursery. He solves it mainly by using Amblyseius swirskii, supplemented with Amblyseius cucumeris in the cold season. He steams to control primarily Fusarium, nematodes and Rhizoctonia. Good hygiene practice during steaming and the stimulation of soil life after steaming are also necessary, he says.

Maurice van Os has a nursery of 2.5 ha in the southwest of the Netherlands and grows the varieties ‘Feeling Green Dark’ and ‘Alana’. The grower comes from a true chrysanthemum family. He started in 1997 as the third generation. His grandfather, father and uncle also grew chrysanthemums at a different location. When the family built a new greenhouse in 1998 his uncle left the company and his father followed later.
The location of the company was deliberately chosen for its 'good' ground: a sufficiently airy soil, with a sandy subsoil containing humus. The good soil structure makes watering easy.
He steams the nursery annually just like his father, uncle and grandfather. They used to hire a steam boiler but in 1998 Van Os purchased a high-pressure steam boiler. In those days heating and steaming with one boiler was the trend but now he wouldn’t purchase such a high-pressure boiler. “The mandatory annual inspection is an extra cost. The advantage is that the soil becomes less wet and the sheet cover over the soil gains a sphere shape faster.”

Steam after the summer

Opinions about the best time to steam vary. The chrysanthemum grower steams annually between week 30 and 39. “Some of my colleagues steam before the holiday. I chose afterwards. After steaming the plants grow better.”
Combined with the greenhouse temperature, which during the summer can rise to more than 32ºC, it can lead to too many buds in the bunch; ten instead of six. “We call that a ‘wild’ stem. In addition, the varieties that I grow are already quite heavy. If we steamed before the summer they would become too heavy. Then you also have more chance of yellow leaves. If the autumn is disappointing then you are very pleased with the heavier stems.”

Steam via the drainage

The chrysanthemum grower laid a steam drainage system 55 cm deep. Before steaming, Van Os loosens the ground to a depth of 50 cm using pens. Then the ground is nice and airy and the steam can spread optimally through the ground. He rolls out the steam sheet with an automatic roller and anchors it at the front and rear with steam chains and the sides with heat proof water pipes. Then the mesh is lowered down and the steam boiler and fan are turned on. The small pipes belonging to the steam drainage system stick out above the cover. The fan sucks the steam through the pipes, pulling it from under the cover deep into the ground.
“I steam for about 6.5 hours. Usually I start steaming as soon as the staff go home at the end of the day. I leave the cover in place and keep the fan running until the next morning.” He uses 3.5 m3 gas per m2 for steaming. Contrary to advice he does not use an extra energy cloth over the steam sheet. “As far as I am concerned, the mesh and supports can also get hot. The steam scorches everything it touches."

Hygiene

Only steaming is not enough according to the grower. Steaming is carried out in one area while the rest of the nursery is in full production. Therefore it is important to ensure that the clean ground is not immediately contaminated again. “Before steaming we thoroughly sweep the path and we ensure that the tilling machine and tractor are clean.”
He purposefully doesn’t partition the greenhouse by lowering the internal walls around the steamed area because he doesn’t believe this helps combat the spread of thrips.

Thrips the biggest problem

Thrips is the biggest problem at the moment. “No one really has the answer.” Every week since the spring he has released Amblyseius swirskii: 200 units per m2. “Every two weeks I take samples to see if there are still plenty of predatory mites in the crop. Many colleagues release Amblyseius cucumeris. I only do that in the colder period from week 48 to week 3. The idea behind the early release of swirskii is that you create a biological balance early in the crop. That tends to work better with swirskii than with cucumeris. So far it doesn't help enough but I don’t need to correct too much in between.”
Before harvesting he sprays the crop clean with Vertimec and Actara.

Quickly bring soil in balance

According to the grower healthy soil leads to more resistant plants, which are essential for reducing the risk of pests and diseases. “After steaming the soil is sterile and the plants, which grow faster have a softer leaf that is extra attractive to thrips. That is not an ideal situation,” says the grower. Therefore once or twice in the winter, between week 40 and week 10, he scatters poultry fertiliser and lime granules to redress the soil balance as quickly as possible. “The fertiliser also helps create an airy soil at the bottom. That’s good because as autumn approaches the ground is wetter.”

Summary

Chrysanthemum grower Maurice van Os uses a high-pressure steam boiler and special steam drainage at a depth of 50 cm to combat Fusarium. He uses Amblyseius swirskii, supplemented with Amblyseius cucumeris in the cold months, to combat thrips. In addition he maintains a healthy soil by ensuring an airy soil structure and applying poultry fertiliser and lime granules after steaming.

Points of attention for steaming

René Corsten of the Delphy chrysanthemum team has some points to remember when steaming the greenhouse:
- Make sure that the ground to be steamed is as dry as possible. Trying to steam wet ground is a waste of energy so stop the watering early enough.
- Use insulation material over the steam sheet. Insulation saves up to 0.5 m3/m2 and there is less condensation under the cover so the ground shuts itself off less quickly especially at the outer edges.
- With a little effort the steam transportation pipes can also be insulated.
- Preferably use rainwater.
- Flushing on time and good water treatment are important for effective steaming.
- Measure the temperature to check what you are achieving. These days good thermometers are available.
- If there is a problem with nematodes or soil fungi aim for 60-60-60: 60 centimetre deep, 60ºC and 60 minutes. The aim is not to use as little gas as possible but to get the best result. Vacuum (suction) steaming is a must. After steaming allow the fan to run for around 12 hours. Then there should be a continuous heating effect to a greater depth.

In a large greenhouse with supplementary lighting the temperature differences in winter can rise so high it’s at the expense of quality and energy consumption. Berg Roses, of Delfgauw, the Netherlands, has already broken new ground with the Next Generation Growing and is fully committed to improving the climate. After a trial with vertical fans it is now running a trial with horizontal fans.

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